The use of lithotripsy in the treatment of kidney stones will soon become widespread. This physical process for the mechanical comminution of renal calculi depends for its effectiveness, in part, on the mechanical properties of such stones. Very recent work has shown that the hardness of certain types of kidney stones can be reduced dramatically by changes in synthetic urine pH. Additional work has also demonstrated that this hardness reduction is reflected in a similar reduction in the stress level required to fracture such stones. These previous investigations only explored the extreme ranges of human urine pH levels and exposure times. The extension of this previous work is proposed to include a full matrix of pH levels and exposure times and to verify by direct sonic testing that such methods increase the ease of fracture of renal calculi by sonic methods. For this investigation both a laboratory scale lithotripter as well as a commercial clinical lithotripter will be used. An analytical model, utilizing measured mechanical properties, of the sonic fracture process will be developed and used to evaluate theoretically the question of whether improved stone fracture by means of controlled shock pulse widths, sonic frequencies, and intensities can be achieved. The expected result of this work is the development of optimum urine pH and exposure conditions to minimize the number of sonic repetitions needed to cause stone comminution with concomitant reduction in patient x-ray exposure and the time required for successful lithotripter treatment.